Therapy-Refractory Progressive Paraneoplastic Sensorimotor Polyneuropathy in a Juvenile Patient with Intracranial Sarcoma

Introduction: Paraneoplastic neurological syndromes are rare but can affect any part of the peripheral nervous system (PNS) including motor neurons, sensory ganglia, nerve roots, plexuses, cranial and peripheral nerves, and neuromuscular junctions. Pathogenesis also varies from direct infiltration by cancer cells, to treatment toxicity, to metabolic derangement, cachexia, infections and paraneoplastic syndromes.

Case Report: We report the case of a 15-year-old male patient who presented with a 4 weeks history of progressive gait instability and neuropathic pain on excertion. Clinical neurological examination showed hyporeflexia of inferior extremities, ataxia, progressive neuropathic pain and predominant distal muscle weakness. An elevated protein concentration without pleocytosis was found in cerebrospinal fluid. Electrophysiological studies revealed a progressive lower extremities axonal neuropathy predominant of the sensory nerves, a demyelinating neuropathy predominant of the motor nerves and a conduction block. The patient received two courses of intravenous immunoglobulin (0.6 g/kg/d) 6 and 8 weeks after symptoms onset without any significant clinical change and continuing progressive polyneuropathy. After 9 weeks of onset of symptoms, a 3-day course of methylprednisolone (1,000 mg/d) was given but the patient’s situation did not improve. Cranial MRI revealed leptomenigeal enhancement including the cranial (V, VII, VIII, IX, X, and bilateral) and spinal nerves, and cranial parenchyma lesions. Extensive diagnostic for autoantibodies was not conclusive. Brain biopsy of the cerebellar lesions revealed histologic finding of small blue round malignant cells compatible with undifferentiated cerebral sarcoma. The patient was treated with polychemotherapy and craniospinal radiation according to the CWS guidance for NRSTS High Risk Group. The tumor lesions decreased but the polyneuropathy-associated symptoms progressed, and 3 months after diagnosis, the patient was no longer able to walk. Immunoadsorption is considered after the end of polychemotherapy.

Conclusion: Paraneoplastic neuropathy is rare in childhood. This case report describes for the first time a therapy refractory clinical course of a paraneoplastic sensorimotor polyneuropathy associated with isolated cerebral sarcoma. As there are presently no established treatment guidelines based on larger cohorts or even randomized controlled trials, therapeutic algorithms and decisions in paraneoplastic neuropathies continue to remain a challenge.